The present invention relates generally to toys, and more specifically to yo-yo's.
Cushions
Most yo-yo bodies are hard and can cause hand pain or injury when they return rapidly. They can also injure noses, furniture, walls and other things that they collide with. There have been a few prior yo-yo's with some attempt at cushioning.
U.S. Pat. No. 3,081,578 (Mosher) is typical of the prior cushion art. Mosher's specification discloses "annular bands." There are several yo-yo's on the current market also offering similar annular rubber bands. However, it appears that these yo-yo's do not provide a sufficient degree of cushioning.
a. The radial thickness of these bands is less than 0.2 inches. Mosher does not give dimensions. However, scaling from Mosher's figures reveals a radial thickness for his annular band 100 of approximately 0.025 inches.
b. The bands are not radially anchored to the body. Rather, they are retained by the elastic tension of the band itself. In order keep the band from flying off due to centrifugal force, these bands are made from a much stiffer rubber than optimum. They are typically made of a material having Shore durometer exceeding 65 A.
The present inventor has evaluated yo-yo's having stiff, radially thin rubber bands and has found them to be useless for cushioning the impact of the yo-yo in the hand. In most cases, manufacturers of these yo-yo's do not claim cushioning. Instead, they state that the rubber bands protect the yo-yo bodies from abrasion on floors and other hard surfaces.
The Henry's yo-yo has bodies made almost entirely from rubber, with the rubber portions being mounted on small metal hubs). These bodies are hollow bell-shaped semispherical shells similar to those found on "Diavlo" toys. The unsupported nature of these rubber shells necessitates that they be made from stiff rubber which detracts from their cushioning benefit.
String Gaps
There are several prior configurations of gap geometry:
a. The most common configuration is a gap with parallel walls which are typically 0.08 to 0.13 inches apart. A disadvantage of this configuration is that narrow gap-entrance often drags on the string which shortens spin time and/or leads to tumbling due to gyroscopic precession.
b. An alternative gap configuration has all or a portion of the gap walls angled so as to increase the gap width at the gap-entrance. Examples of angled gap configurations can be found in U.S. Pat. Nos. 3,953,936, 4,130,962 (both by Ennis) and U.S. Pat. No. 3,175,326 (Isaacson).
c. U.S. Pat. Nos. 207,527 (Katz) and 271,278 (Schoenfeld) disclose convex gap walls with spherical contours like the surface of a convex lens. This configuration also yields a widened gap-entrance.
d. There are also a number of "butterfly" yo-yo's on the market which have parallel gap walls but a large-radius mouth to widen the gap entrance.
Features to Facilitate Return
Most yo-yo's have short radial ribs to roughen the string-gap walls adjacent to the axle. The ribs catch the string when the user jerks the string to make the yo-yo wind thus return. When the yo-yo sleeps (spinning at the end of the string) the ribs rub the string, making noise and reducing spin time and string life.
Spintastics Corporation has manufactured yo-yo's which have a step in each gap wall adjacent to the axle. These steps have a radial dimension extending 0.115 inches outward from the axle or bearing.
Axle Types
Yo-yo's are made with either fixed axles or with rotating bearings, called transaxles. The string is wound in the gap either directly around the fixed axle, or around a transaxle bearing which surrounds the axle. Transaxle bearings are either sleeve (journal) bearings or ball bearings. Transaxle yo-yo's sleep (spin) longer than fixed axle yo-yo's but are generally inferior for looping tricks. The string gap design is more critical for transaxle yo-yo's than for fixed axle yo-yo's because there is greater dependency on the string's grabbing the gap walls to facilitate return.
Advanced transaxle yo-yo users apply viscous grease adjacent to the bearing to create some drag in order to retard sleep and facilitate return during looping. They add more grease and change the string every ten to fifteen minutes of play. The grease makes it difficult to properly execute most non-looping tricks.
Assembly Method
The simplest yo-yo's comprise fixed assemblies with the axle rigidly fixed to the body elements. More advanced yo-yo's are screwed together to permit disassembly in order to remedy string tangles. Virtually all yo-yos of this category use the following method of assembly. The axle is threaded at both ends. Each end screws into a nut set in a mating socket in the body. The body elements are then rotated relative to each other to screw them on to the threaded ends of the axle. The torque that can be developed, even by a child, when rotating the body elements is high enough to shear off the threaded end of the axle. An added problem is that the body elements often unscrew in normal use. When this happens the yo-yo suddenly comes apart in mid-trick and parts scatter over a wide area. Often some of the parts become lost.
Gap Width and Adjustability
The majority of commercial yo-yo's have fixed width gaps. However, as mentioned above, transaxle yo-yo's are generally inferior for looping tricks. In an effort to correct this problem some transaxle yo-yo's have been offered with adjustable width gaps.
An early method of adjustment required the user to disassemble the yo-yo and insert or remove spacer washers. Some later yo-yo designs have offered the more convenient method of varying the gap by rotating the left and right body elements relative to each other. Rotation screws the body elements closer or farther apart. However, inadvertent rotation (if the yo-yo collides with an object) can still cause the yo-yo to disassemble or change gap setting during use.